Answer:b
Justinian’s Difficulties
A terrible plague swept through the empire, killing Theodora and almost killing him. The plague wiped out huge numbers of the empire’s population, leaving villages empty and crops unharvested. The army was also afflicted, and the Ostrogoths were able to effectively regain Italy in 546 CE, through guerrilla warfare against the Byzantine occupiers.
With Justinian’s army bogged down fighting in Italy, the empire’s defenses against the Persians on its eastern frontiers were weakened. In the Roman-Persian Wars, the Persians invaded and destroyed a number of important cities. Justinian was forced to establish a humiliating 50-year peace treaty with them in 561 CE.
Still, Justinian kept the empire from collapse. He sent a new general, Narses, to Italy with a small force. Narses finally defeated the Ostrogoths and drove them back out of Italy. By the time the war was over, Italy, once one of the most prosperous lands in the ancient world, was wrecked. The city of Rome changed hands multiple times, and most of the cities of Italy were abandoned or fell into a long period of decline. The impoverishment of Italy and the weakened Byzantine military made it impossible for the empire to hold the peninsula. Soon a new Germanic tribe, the Lombards, came in and conquered most of Italy, though Rome, Naples, and Ravenna remained isolated pockets of Byzantine control. At the same time, another new barbarian enemy, the Slavs, appeared from north of the Danube. They devastated Greece and the Balkans, and in the absence of strong Byzantine military might, they settled in small communities in these lands.